The present invention relates generally to vacuum gate valves, and more particularly to a vacuum gate valve including a first valve plate movable perpendicularly to the valve axis and a second valve plate, and a spreading mechanism arranged between the valve plates for moving the valve plates between an open position and a closed position of the valve.
Vacuum gate valves with spreading mechanisms of various types are described, illustrated and explained in German Offenlegungsschrift No. 30 28 786. The spreading mechanisms illustrated in this case include surface areas which roll against one another when the valve is actuated, the rolling action sometimes taking place under high pressure. Since these surface areas are located in a vacuum and, therefore, are entirely without lubrication, these rolling movements lead to substantial wear. With increasing wear, the quality of the usually expensive valve is significantly reduced within a short period of time. The wear increases with increased specific surface pressures. When balls or spheres are used as rolling members, these specific surface pressures become very high.
Therefore, it is the primary object of the present invention to provide a gate valve of the above-described type, wherein the structural components of the spreading mechanism have linear contact with one another during their operation, so that they move relative to one another practically without generating any friction, and wherein the contact surfaces between the structural components of these mechanisms are as large as possible in the closed position of the valve, i.e., when the highest load is applied to the components.
Another object of the invention is to provide a gate valve wherein the spreading mechanism is capable of keeping the closed valve in the closed position without requiring external forces which might be subject to failure, such as, forces generated electrically, magnetically, hydraulically or pneumatically.